There is a growing trend toward all-optical re-configurable networks promising higher levels of data-rate and protocol transparency. However, in order to maintain these higher performance levels, signal quality monitoring must be provided at the optical layer. In such systems measurement of optical parameters is critical as it provides vital information regarding the performance of the system. Such information can then be used for diagnosis and repair of an optical network or for performance of optimization actions. One standard measurement of signal quality in optical systems has been the bit error rate (BER) of a system. The BER of a system is affected by two forms of signal degradation, noise and distortion. The measurement of such parameters must be accurate, have a wide range, and be performed in a timely manner so as to provide the necessary information in the shortest amount of time for the appropriate actions.
Some techniques used for monitoring optical signal quality include spectral analyzing and sampling. The conventional approach to analyzing the optical parameters of a spectrally dependent system is to use an optical spectrum analyzer. These systems are generally based on an optical tool known as a monochromater. Monochromater-based optical spectrum analyzers are typically slow, large in size for most embedded and field applications, and tend to drift with time, giving poor absolute accuracy. The sampling method on the other hand, is the only method that accounts for both noise and distortion and thus comes closest to BER measurement. Unfortunately, previous implementations of sampling methods have been very complicated, slow, and are limited to a single data rate and a single protocol.